Question

In a chemistry lab, you have 2 vinegars. One is 5% acetic acid, and one is 6.5% acetic acid. You want to make 200 ml of a vinegar with 6% acetic acid. How many milliliters of each vinegar do you need to mix together? Model this situation with a system of equations and solve.

Answer 1

We have 5% and 6.5% acetic acid solutions and we need 200 ml of 6% acetic acid.
Set up two equations:
f means 5% and s means 6.5%
A) f + s = 200
B) .05f + .065s = (.06 * 200)
Multiplying equation A by -.05
A) -.05f  -.05s = -10
B) .05f + .065s = 12 then adding both equations:
.015s = 2
we need 133.33 ml of 6.5% acetic acid and
66.67 ml of 5% acetic acid solution.
 
Source:
http://www.1728.org/mixture.htm